1. Technical Field
The present invention relates to a liquid ejecting head that includes a piezoelectric element comprising piezoelectric film formed from a piezoelectric material and electrodes and discharges liquid droplets from a nozzle opening, a liquid ejecting apparatus, and a piezoelectric element.
2. Related Art
As a representative example of a liquid ejecting head, for example, there is an ink jet type recording head in which a part of a pressure generating chamber communicating with nozzles ejecting ink droplets is constituted by a vibration plate, the vibration plate is deformed by a piezoelectric element, and ink in the pressure chamber is pressurized and discharged from nozzles as ink droplets. The piezoelectric element used for the ink jet type recording head, is made from electromechanical a piezoelectric material characterized with conversion, for example, a piezoelectric film inserted between two electrodes.
As methods of forming piezoelectric film, there are chemical solution methods, such as sol-gel, MOD (Motel Organic Deposition) method and so on, and physical method, such as sputtering method. Piezoelectric film can be created using these methods. For example, in case of using sol-gel method, organic metal compounds are dissolved in solvent to form colloidal solution, then it is coated on a substrate, the formed film is heated and crystallized to form a piezoelectric film.
As a piezoelectric material used in the piezoelectric element, generally, for example, a lead-based piezoelectric ceramic represented by lead zirconate titanate (PZT) has been used (for example, see JP-A-2001-223404). However, from the viewpoint of environmental problems, there has been a demand for a piezoelectric material which is lead-free or has a restricted lead content. As a piezoelectric material that does not contain lead, a barium titanate-based complex oxide has been known from the past (see JP-A-62-154680).
However, barium titanate-based composition has been mainly used as a piezoelectric bulk material. There is almost no practical study on barium titanate-based piezoelectric film formed on a substrate by using chemical method or physical method. In addition, barium titanate-based ceramic is fabricated by mixing powder of metal oxides or metal carbonate at first, then calcining, grinding, forming the mixture and firing the formed body at 1000-1400° C., finally making electrode on polished both sides of the ceramic. Therefore, stress caused by volume expansion and contraction of the ceramic at the time of manufacture is significantly small compared with that caused at the time of forming a piezoelectric film on a substrate by chemical solution method or sputtering method.
If the barium titanate-based material is used for a piezoelectric film on a substrate, there is a problem in that displacement is significantly small compared with that of the above-described PZT. It is also desirable to meet the needs of increasing density of barium titanate-based film, firing the film at low temperature and so on.
The present inventer has found a barium titanate-based composition containing barium, titanium as well as copper equal to or less than 3 mol % of titanium amount, lithium more than or equal to 2 mol % and less than or equal to 5 mol % of titanium amount, and boron more than or equal to 2 mol % and less than or equal to 5 mol % of titanium amount, from which a dense film with large piezoelectric displacement can be formed at low temperature. However, the obtained film with above-mentioned composition shows a relatively high leakage current. In addition, such a problem also occurs to other piezoelectric elements without being limited to a liquid ejecting head represented by an ink jet type recording head.